A standard machinist's vise has a housing block that is normally bolted to the bed of the machine being used, a fixed jaw essentially integral with this block, a movable jaw slidable in a longitudinal direction on the block toward and away from the fixed jaw, and a threaded spindle for effecting this movement. One end of the spindle normally engages in a bearing in the block or fixed jaw and is threaded in a nut in the movable jaw and this spindle extends parallel to the vice-closing and -opening direction so that rotation of the spindle in one direction moves the jaws, that is it does not engage them at locations generally centered above the spindle axis, the jaws tend to cant or twist relative to one another and to the housing block. Since such a vice typically is used to exert considerable force, this offcenter action can distort much of the structure of the vise. In particular the spindle can be deformed or wedged in its bearing in the block or its nut in the movable jaw. In order to prevent the device from binding, it is therefore necessary to manufacture the guides in the housing block, the corresponding parts of the movable jaw, the spindle, and the nut to very close tolerances so that such twisting is not concentrated as a force in one location.
Even a very carefully constructed such vise can, however, bind and deform when an offcenter workpiece is clamped very tightly. This can lead to premature wear of the spindle, and generally makes it difficult to tighten and loosen the vise.